This invention relates to refrigerant charging systems, and more particularly, to a control system for controlling the charging of refrigerant into a refrigerant system.
In the past, a number of charging systems and techniques have been used to charge refrigerant into refrigerant systems, such as cooling systems. These systems can be as simple as a set of hoses and gauges which are used to connect a tank of pressurized refrigerant to the refrigerant system. Refrigerant is then charged into the refrigerant system until a desired pressure is reached. Outside the automotive industry, the use of hose and gauge sets is perhaps the most common way of charging refrigerant into refrigerant systems.
In the automotive industry, a number of systems have been used to charge refrigerant into refrigerant systems, i.e., the air conditioning systems on the automobiles, including the hose and gauge sets. While the hose and gauge sets are truly portable in the sense that they can be picked up and carried from job to job by hand, more complex systems are portable only in the sense that they are built in carts that can be wheeled from job to job.
One such refrigerant charging system that has been used in the past is described in U.S. Pat. No. 3,873,289 for an Air Conditioner Servicing United to Kenneth R. White, the president of K-Whit Tools, Inc, the owner of this application. The apparatus disclosed in the '289 patent charges refrigerant through a pressure compensated constant flow valve and controls the amount of refrigerant charged into the refrigerant system by a timer. In this manner, the charging system disclosed in the '289 patent achieves the desirable objective of accurately controlling the amount of refrigerant charged into the refrigerant system being charged.
While the system disclosed in the '289 patent has been successfully marketed for many years by the assignee of this application, one problem that it has is that the mass of refrigerant which flows through the constant flow valve in a given unit of time will vary from refrigerant type to refrigerant type. Moreover, it will also vary with pressure which in turn varies with temperature. Controlling the mass of refrigerant charged and being able to determine the mass of refrigerant charged is desirable since mass or weight is typically used both for inventory purposes and for determining the cost of the recharging service.
In addition to being able to accurately determine the mass of refrigerant charged into a refrigerant system, it is also desirable to be able to charge a given amount of refrigerant into a refrigerant system. Often, when recharging a refrigerant system, the service technician will take appropriate measurements, such as inlet and outlet pressures, and determine the amount of refrigerant that needs to be recharged into the system. Alternatively, the service technician may choose to charge the refrigerant system to a given pressure in which case it is important that the service technician be able to determine the amount of refrigerant charged into the system for the reasons discussed previously.
Another problem with systems of the type described in the '289 patent is that they are only "semi" portable. They are mounted in carts and while they can be rolled from job to job in a confined area, such as in an automotive repair garage, they cannot be easily moved from site to site such as is required to service home and commercial refrigerant systems. For this reason, hose and gauge sets are still the system of choice in servicing refrigerant systems outside the automotive industry. However, hose and gauge sets are manual systems which rely solely upon the judgement of the service technician to determine when the refrigerant system has been adequately charged. Moreover, they do not provide for a way of determining the amount of refrigerant charged into a system, although sometimes scales are used with hose and gauge sets to determine this.
It is an object of this invention to provide a control system for controlling the charging of refrigerant into a refrigerant system that has a constant flow valve and determines the mass of refrigerant charged based on the volume of refrigerant that has flowed through the valve, the refrigerant type, and the pressure of the refrigerant being charged into the refrigerant system.
It is also an object of this invention to provide a control system for controlling the charging of refrigerant into a refrigerant system that allows the service technician to preset the amount of refrigerant to be charged into the refrigerant system and which will then charge that amount of refrigerant into the refrigerant system.
It is also an object of this invention to provide a truly portable, i.e., hand carried, control system for controlling the charging of refrigerant into a refrigerant system.
It is also an object of this invention to provide a mass flowmeter for gaseous fluids which a constant flow valve throught which the gaseous fluid flows and which determines the mass amount of gaseous fluid based on the volume of gaseous fluid that has flowed through the constant flow valve and the density of the gaseous fluid as determined by the pressure of the gasous fluid at the outlet of the constant flow valve and data related to the density characteristics of the gaseous fluid.